ZyXEL XGS4700-48F User Guide - Page 285

CHAPTER 27 Loop Guard This chapter shows you how to configure the Switch to guard against loops on the edge of your network. 27.1 Loop Guard Overview Loop guard allows you to configure the Switch to shut down a port if it detects that packets sent out on that port loop back to the Switch. While you can use Spanning Tree Protocol (STP) to prevent loops in the core of your network. STP cannot prevent loops that occur on the edge of your network. Figure 134 Loop Guard vs STP STP Loop Guard Loop guard is designed to handle loop problems on the edge of your network. This can occur when a port is connected to a Switch that is in a loop state. Loop state occurs as a result of human error. It happens when two ports on a switch are connected with the same cable. When a switch in loop state sends out broadcast messages the messages loop back to the switch and are re-broadcast again and again causing a broadcast storm. If a switch (not in loop state) connects to a switch in loop state, then it will be affected by the switch in loop state in the following way: • It will receive broadcast messages sent out from the switch in loop state. XGS4700-48F User's Guide 285